The invention relates to a sealing arrangement between two cylindrical bodies which can be moved relative to one another. One body has a seat for receiving a sealing ring made of elastic material and which, with the two bodies in a state of rest, has a given clearance with respect to the sealing surface of the other body. At least one side of the ring forms an angle with the corresponding side of the seat in order to permit the sealing ring, under the action of the pressure of a fluid penetrating the free space between the two bodies on one side of the seat, to rotate about its torsional axis and thereby engage against one of the two sides of the seat which serve as sealing surfaces.
Arrangements of this general type are already known. For example, in Swiss Pat. No. 560,340 there is disclosed an arrangement in which an annular seal has a V-shaped cross-section along its periphery, while the ring gasket has a cross-section substantially formed by sides which converge towards the base of the seat. In this known arrangement, the opening angle of the seat is larger than the angle of the two sides of the gasket ring which converge from the contact surface of the gasket ring facing the sealing surface of the other body towards the tip thereof on the bottom of the slot-like seat. Thus, the spacing between the two sides of the seat measured at a certain radial distance from the longitudinal central axis of the cylindrical body and the gasket ring is always greater than the corresponding spacing between the sides of the gasket ring. If necessary, the gasket ring can be in contact in the rest state with the sealing surface of the other body with which it must perform its sealing function or must be at a limited distance from that sealing surface. Furthermore, the gasket ring must rest without any pressure on the base of the annular seat, because it would otherwise be in an unstable state of equilibrium and, due to the pressure, would be drawn against one or the other side of the seat instead of being positioned symmetrically to the seat as is in the present case. If a pressurized fluid now enters the free space formed by one side of the seat and the corresponding side of the gasket ring, forces are exerted on the gasket ring which result in a torque distributed over the annular torsional axis of the gasket ring. In practice, the pressurized fluid moves the gasket ring by a unit by an amount dependent upon the existing clearance until the tips of the lower lips, with which the gasket ring is supported on the base of the seat, come into contact with the corresponding side of the annular seat. This contact produces a reaction by the seat side on the gasket ring which leads to a rotation of the ring about its torsional axis to cause one or other of the outer tips of the gasket ring to rise, i.e. to increase its radial spacing. This lift or increase of spacing then brings about contact with the sealing surface of the facing body, accompanied by a corresponding sealing action.